Re: Circular polarizer question

"SayWhat" <spamless@xxxxxxxx> wrote in message
news:alec83h4to8dkrui9isk7c9mbipi08uqpg@xxxxxxxxxx
On Fri, 29 Jun 2007 11:01:39 -0700, lphilpot <len@xxxxxxxxxxx> wrote:

I have a brand new Tiffen 72mm circular polarizer I purchased with my
new Rebel XT. I've not yet shot any images through it, but simply
looking through it outdoors under a partly (cumulus) cloudy but
otherwise blue sky, it appears to have virtually no apparent
polarizing effect. I have two other standard non-circular polarizers
(a 55mm Bower and a 49mm Rolev) and they both make a significant
difference in the sky, in removing reflections from a car window,
etc., etc. as expected. However, a view through the TIffen and either
of the other two will go nearly black as expected when properly
rotated. That tells me the TIffen is indeed polarizing as it should
(maybe?).

This is the first circular polarizer I've owned and Tiffen is a
reasonable brand. Is this normal for a circular polarizer, or is there
something wrong with it?

Thanks!

Out of all the polarizers I've ever tested, Tiffens' always come in
dead-last as
far as polarizing strength goes. Not only that, but the polarizing
substrate is
often uneven showing strong banding effects, when tested by crossing it at
90-degrees against a lab-quality polarizer that I use for these purposes.
Some
even display blank areas and smaller striations. I have a $12 generic
polarizer
that beats out a $70 Tiffen. They figure people won't test them so they
can get
away with it. You don't always get what you pay for these days, sometimes
you
just get taken to the cleaners by popular brand names that charge a
fortune to
make you THINK you are getting quality.


I have a Tiffen and holding it up to my LCD, at the darkest position, it
still lets some blue light through. It is several stops less than when
turned 90 deg, so should be quite effective for photography use. OTOH, I
have a Promaster polarizer. It blocks more completely in the same test, but
has a problem of its own: With it on my 80-200 lens @ 200mm my camera was
unable to AF well. After taking some shots, I found there was no point of
focus. Next, I held the filter in front of my binoculars, and noticed
blurring distortion that turned when I turned the filter. Turns out the
filter is not perfectly flat and causes astigmatism. Total crap.

Anyone try the cheap "Targus" brand CPL? I bought a 52 and 58mm each for
$13. I tested them and they filter well and do contain the quarter wave
plate. The down side is they do not include cases.
John


.

Relevant Pages

  • Re: Playing with polarisers- color effects
    ... quarter-wave plate is only a quarter-wave plate at one wavelength, ... as you depart from that wavelength, ... In the visual wavelengths, the polarizer is extremely good, effectively 100%, so crossing them gets rid of all that light. ... But at the shortest wavelengths the filter is less than 100% effective, so that crossing two of them will still transmit a bit of unpolarized purple light. ...
    (rec.photo.digital)
  • Re: polariser filter
    ... Filter is defective. ... It's always been a pot-shot buying polarizers by brand name. ... and with luck you'll get a polarizer worth 2x's what that Hoya cost ... purchased filter materials. ...
    (rec.photo.digital)
  • Re: "Sports" Polarizer
    ... It was is NOT to be confused with the current circular ... filter was circular. ... Since most scenes are illuminated from above on average, the linear polarization present in reflected light will be tend be horizontal in direction. ... A cilcular polarizer consists of a linear polarizer, which does the required filtering, followed by a quarter-wave retarder, which converts the linearly-polarized light to circularly-polarized light, which behaves better inside a camera with internal reflections. ...
    (rec.photo.digital)
  • Re: Differences in Polarizers?
    ... But is there a difference in the effects of the polarizer, ... look through the filter held at arm's length, ... take two polarizers and stack them, then rotate them ... polarizer out on the sky. ...
    (rec.photo.technique.nature)
  • Re: Using Polarizing Filter With Skylight Filter
    ... the polarizer or the lens itself. ... How much does a polarizer degrade the image compared to a skylight filter? ... lens hood might afford all the protection you need, ...
    (rec.photo.equipment.35mm)